Would a pair of 4 ohm resistors protect my radio and allow me to use 4 ohm speakers.
11-19-2010, 12:14 PM
#1
Le Mans Master
Thread Starter
Would a pair of 4 ohm resistors protect my radio and allow me to use 4 ohm speakers.
If I soldered in line a pair of radio shack 4 ohm resistors, would that work and allow me to use a set of 4 ohm speakers. The original part shown below I guess would be removed and saved. Would this be safe for the correct radio in a 68. I like the correct look in the dash, but I would like to get new speakers. At the moment I dont have any, and I cant drop 4-5 hundred on bringing the radio up to todays standards, or just purchase the correct ohm speakers. Thank you in advance. 
11-19-2010, 12:27 PM
#2
Le Mans Master
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if you use resistors to increase total load, two things have to be kept in mind. half of the power(volume) will be disipated by the resistors, so you'll have to set the volume much higher to hear the radio over the rattles, squeaks and rumbles. and, you'll have to find resistors of the correct wattage-i'd guess at least 20 watts. that's not going to be easy. better yet, go to auto zone and buy two additional 4 ohm speakers (about $10 each) and wire two speakers in series for each side. mount the extra speakers in the kick area. just wire them + to - in order to keep the phase correct. if the speakers aren't maked for polarity, get a 1 1/2 volt flashlight battery and touch the speaker lugs and watch if the cone moves in or out. then just mark the speakers according to the battery.
Last edited by jnb5101; 11-19-2010 at 12:29 PM.
11-19-2010, 12:53 PM
#3
isnt the picture the power transistor for the radio? what has that to do with the ohm rating of the speakers?
11-19-2010, 12:59 PM
#4
Burning Brakes
if you use resistors to increase total load, two things have to be kept in mind. half of the power(volume) will be disipated by the resistors, so you'll have to set the volume much higher to hear the radio over the rattles, squeaks and rumbles. and, you'll have to find resistors of the correct wattage-i'd guess at least 20 watts. that's not going to be easy. better yet, go to auto zone and buy two additional 4 ohm speakers (about $10 each) and wire two speakers in series for each side. mount the extra speakers in the kick area. just wire them + to - in order to keep the phase correct. if the speakers aren't maked for polarity, get a 1 1/2 volt flashlight battery and touch the speaker lugs and watch if the cone moves in or out. then just mark the speakers according to the battery.
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11-19-2010, 01:07 PM
#5
Le Mans Master
Thread Starter
11-19-2010, 03:45 PM
#6
Le Mans Master
Speakers are rated in ohms of (AC) "impedance". Resistors are rated in ohms of (DC) "resistance". They are not the same thing. If you measure ohms across the voice coil of a speaker with an ohmeter (VOM), you are using the DC battery inside the meter to apply DC across the coil... and you measure DC resistance (close to 0)... not impedance. Try here... http://www.hometoys.com/htinews/feb0.../impedence.htm
11-19-2010, 03:53 PM
#7
no matter what you do with the speakers the radio wont work without the power transistor you cannt get rid of it
11-19-2010, 03:56 PM
#8
Melting Slicks
if you use resistors to increase total load, two things have to be kept in mind. half of the power(volume) will be disipated by the resistors, so you'll have to set the volume much higher to hear the radio over the rattles, squeaks and rumbles. and, you'll have to find resistors of the correct wattage-i'd guess at least 20 watts. that's not going to be easy. better yet, go to auto zone and buy two additional 4 ohm speakers (about $10 each) and wire two speakers in series for each side. mount the extra speakers in the kick area. just wire them + to - in order to keep the phase correct. if the speakers aren't maked for polarity, get a 1 1/2 volt flashlight battery and touch the speaker lugs and watch if the cone moves in or out. then just mark the speakers according to the battery.
Resistors would up the impedance to a safe level for your radio but would waste power, half the output would be disipated by the resistors as JNB5101 stated.
11-19-2010, 05:15 PM
#9
Race Director
like...omg..... sold car stereo systems for ~5 years.... put the speakers in, no resistors, and you will have no problems.... the only reason to make sure your polarity is correct is for better base, it has to do with phasing, ........... you will not have any problems hooking up a 4 ohm speaker in a 8 ohm system... the resistance is for the amplifier load. you will be fine.
w=v^2/r so, a lower resistance makes the amp work harder... but in this case not hard enough to hurt anything...
btw... a lot of incorrect information on this thread.
w=v^2/r so, a lower resistance makes the amp work harder... but in this case not hard enough to hurt anything...
btw... a lot of incorrect information on this thread.
Last edited by pauldana; 11-19-2010 at 05:21 PM.
11-19-2010, 05:34 PM
#10
Melting Slicks
What information did you find technically inaccurate?
All I've seen is technically true. Whether the system tolerates it is the question. These old radios were not 8 ohm systems, they were something odd like 10 ohms, don't recall exactly. A 4 ohm speaker will work the amp harder. Could be within tolerable limits but I'm not sure I'd want to find out at expense of my power transistors. Some risk. Up to the OP.
Yes, the phasing has to do with BASS, keeping the wave in phase so output of one doesn't cancel the other. Whether it's noticeable in a car, don't know...
All I've seen is technically true. Whether the system tolerates it is the question. These old radios were not 8 ohm systems, they were something odd like 10 ohms, don't recall exactly. A 4 ohm speaker will work the amp harder. Could be within tolerable limits but I'm not sure I'd want to find out at expense of my power transistors. Some risk. Up to the OP.
Yes, the phasing has to do with BASS, keeping the wave in phase so output of one doesn't cancel the other. Whether it's noticeable in a car, don't know...
11-19-2010, 06:35 PM
#11
Melting Slicks
like...omg..... sold car stereo systems for ~5 years.... put the speakers in, no resistors, and you will have no problems.... the only reason to make sure your polarity is correct is for better base, it has to do with phasing, ........... you will not have any problems hooking up a 4 ohm speaker in a 8 ohm system... the resistance is for the amplifier load. you will be fine.
w=v^2/r so, a lower resistance makes the amp work harder... but in this case not hard enough to hurt anything...
btw... a lot of incorrect information on this thread.
w=v^2/r so, a lower resistance makes the amp work harder... but in this case not hard enough to hurt anything...
btw... a lot of incorrect information on this thread.
11-19-2010, 07:05 PM
#12
Race Director
What information did you find technically inaccurate?
All I've seen is technically true. Whether the system tolerates it is the question. These old radios were not 8 ohm systems, they were something odd like 10 ohms, don't recall exactly. A 4 ohm speaker will work the amp harder. Could be within tolerable limits but I'm not sure I'd want to find out at expense of my power transistors. Some risk. Up to the OP.
Yes, the phasing has to do with BASS, keeping the wave in phase so output of one doesn't cancel the other. Whether it's noticeable in a car, don't know...
All I've seen is technically true. Whether the system tolerates it is the question. These old radios were not 8 ohm systems, they were something odd like 10 ohms, don't recall exactly. A 4 ohm speaker will work the amp harder. Could be within tolerable limits but I'm not sure I'd want to find out at expense of my power transistors. Some risk. Up to the OP.
Yes, the phasing has to do with BASS, keeping the wave in phase so output of one doesn't cancel the other. Whether it's noticeable in a car, don't know...
11-19-2010, 07:14 PM
#13
Melting Slicks
pauldana may be correct, the OP could connect a 4 ohm speaker without any problem, at least for a while. The lower impedance will draw more current, cause the output stage to heat up a bit more. If the output stage was designed to be robust, it may never be a problem. Even in the worst case, connect a piece of wire to the output, it may not fail for a period of time. I don't know the range of impedances an old radio like this can safely drive, better off asking someone who services them if you wish to deviate from stock or just try it if you're willing to take the chance. Aftermarket radios are often designed to accept a range of loads depending on how the user chooses to configure the system. Typically 4 to 8 ohms as pauldana stated. Wouldn't necessarily bet on it with an old OEM radio.
11-19-2010, 07:34 PM
#14
Drifting
Not all AMPs will handle a 2 ohm set up. I DJ and I run a 4ohm system and use AMPs that can take a 2ohm set up just incase an AMP goes down and one of the other AMPs has to be wired from it's 4ohm set up to a two ohm configuration to keep all the speakers running. Crown amps are one that will take a 2ohm set up.
SO, I wouldn't be concerned unless you get it wired into a 2ohm system. 4,6,or 8 ohm systems usually won't damage equipment.
SO, I wouldn't be concerned unless you get it wired into a 2ohm system. 4,6,or 8 ohm systems usually won't damage equipment.
11-19-2010, 08:23 PM
#15
Team Owner
You can stick a 4 ohm speaker where a 10 ohm unit is supposed to be. It will work just fine...until you get to about 1/2 volume (power). Then the signal will begin to distort, and the louder you make it the more distorted it will be. If you turn it up most of the way and leave it there, the output stage of the amp will burn up [whether some believe it or not]. The real questions is "Why would you want to do such a thing if you already know better?" And someone in the car stereo business bragging about sticking the wrong impedence speakers into customer's cars (obviously without their knowledge)? What's that about??? 
Sounds like a place that I wouldn't want to visit, and one that didn't know what it was doing. {I'm just sayin'....}
The impedence of the speaker is intended to match the output impedence of the amplifier, in order to maximize output efficiency and minimize distortion. You can always use a speaker with a larger impedence than required; the downside is that you lose volume (output power). Using a speaker with too small an impedence is like putting 1" diameter header pipes on an engine designed to have 2" pipes. If you use too much throttle (for very long), it ain't going to be pretty.
Sounds like a place that I wouldn't want to visit, and one that didn't know what it was doing. {I'm just sayin'....}The impedence of the speaker is intended to match the output impedence of the amplifier, in order to maximize output efficiency and minimize distortion. You can always use a speaker with a larger impedence than required; the downside is that you lose volume (output power). Using a speaker with too small an impedence is like putting 1" diameter header pipes on an engine designed to have 2" pipes. If you use too much throttle (for very long), it ain't going to be pretty.
11-19-2010, 09:01 PM
#16
Le Mans Master
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Lets get this straight-
4 ohm speakers? - It means the rating AVERAGES 4 ohms across the audio spectrum (20hz- 20Khz)- At 40 hz it might be 2ohms and at 10kHz it might be 12ohms.
These old radios are more finicky then the ones Paul installed in the 80's.
I would not run the 4ohms- unless you do so in a series and add another pair...
Phase - yes, it's more noticable at low frequencies- you can simply turn the balance to the left ( or right) if you get more bass- then the speakers are out of phase. HOWEVER out of phase (180 degress- hooking the polarity opposite) affects ALL the frequencies..One speaker is moving forward- the other backward.
4 ohm speakers? - It means the rating AVERAGES 4 ohms across the audio spectrum (20hz- 20Khz)- At 40 hz it might be 2ohms and at 10kHz it might be 12ohms.
These old radios are more finicky then the ones Paul installed in the 80's.
I would not run the 4ohms- unless you do so in a series and add another pair...
Phase - yes, it's more noticable at low frequencies- you can simply turn the balance to the left ( or right) if you get more bass- then the speakers are out of phase. HOWEVER out of phase (180 degress- hooking the polarity opposite) affects ALL the frequencies..One speaker is moving forward- the other backward.
11-19-2010, 09:29 PM
#17
Team Owner
You can stick a 4 ohm speaker where a 10 ohm unit is supposed to be. It will work just fine...until you get to about 1/2 volume (power). Then the signal will begin to distort, and the louder you make it the more distorted it will be. If you turn it up most of the way and leave it there, the output stage of the amp will burn up [whether some believe it or not]. The real questions is "Why would you want to do such a thing if you already know better?" And someone in the car stereo business bragging about sticking the wrong impedence speakers into customer's cars (obviously without their knowledge)? What's that about??? Sounds like a place that I wouldn't want to visit, and one that didn't know what it was doing. {I'm just sayin'....}
The impedence of the speaker is intended to match the output impedence of the amplifier, in order to maximize output efficiency and minimize distortion. You can always use a speaker with a larger impedence than required; the downside is that you lose volume (output power). Using a speaker with too small an impedence is like putting 1" diameter header pipes on an engine designed to have 2" pipes. If you use too much throttle (for very long), it ain't going to be pretty.
Sounds like a place that I wouldn't want to visit, and one that didn't know what it was doing. {I'm just sayin'....}The impedence of the speaker is intended to match the output impedence of the amplifier, in order to maximize output efficiency and minimize distortion. You can always use a speaker with a larger impedence than required; the downside is that you lose volume (output power). Using a speaker with too small an impedence is like putting 1" diameter header pipes on an engine designed to have 2" pipes. If you use too much throttle (for very long), it ain't going to be pretty.
Lets get this straight-
4 ohm speakers? - It means the rating AVERAGES 4 ohms across the audio spectrum (20hz- 20Khz)- At 40 hz it might be 2ohms and at 10kHz it might be 12ohms.
These old radios are more finicky then the ones Paul installed in the 80's.
I would not run the 4ohms- unless you do so in a series and add another pair...
Phase - yes, it's more noticable at low frequencies- you can simply turn the balance to the left ( or right) if you get more bass- then the speakers are out of phase. HOWEVER out of phase (180 degress- hooking the polarity opposite) affects ALL the frequencies..One speaker is moving forward- the other backward.
4 ohm speakers? - It means the rating AVERAGES 4 ohms across the audio spectrum (20hz- 20Khz)- At 40 hz it might be 2ohms and at 10kHz it might be 12ohms.
These old radios are more finicky then the ones Paul installed in the 80's.
I would not run the 4ohms- unless you do so in a series and add another pair...
Phase - yes, it's more noticable at low frequencies- you can simply turn the balance to the left ( or right) if you get more bass- then the speakers are out of phase. HOWEVER out of phase (180 degress- hooking the polarity opposite) affects ALL the frequencies..One speaker is moving forward- the other backward.
the comments about PHASE are funny, in a car....front/rear/side-side....who can tell what??
lowest note you can hear is about 80 hz doubled....
11-20-2010, 12:26 AM
#18
Race Director
like...omg..... sold car stereo systems for ~5 years.... put the speakers in, no resistors, and you will have no problems.... the only reason to make sure your polarity is correct is for better base, it has to do with phasing, ........... you will not have any problems hooking up a 4 ohm speaker in a 8 ohm system... the resistance is for the amplifier load. you will be fine.
w=v^2/r so, a lower resistance makes the amp work harder... but in this case not hard enough to hurt anything...
btw... a lot of incorrect information on this thread.
w=v^2/r so, a lower resistance makes the amp work harder... but in this case not hard enough to hurt anything...
btw... a lot of incorrect information on this thread.
11-20-2010, 09:01 AM
#20
Le Mans Master
Thread Starter
Thank you for all the information provided, and yes its the original style radio I am talking about. I think I will hide a 2nd pair of speakers in series in the car if thats what it will take. Appreciate your help.